1、 Copyright 2008 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved April 18, 2008 Table of Contents Page Foreword . 2 Introduction . 2 1 Scope 3 2 Conformance Notation 3 3 Normative References 3 4 Nomenclature 4 5 Recommend
2、ed Coding Ranges 4 6 Backward Compatibility. 6 Annex A Bibliography (Informative) 7 Page 1 of 7 pages RP 202-2008Revision of RP 202-2000 SMPTE RECOMMENDED PRACTICE Video Alignment for Compression Coding RP 202-2008 Page 2 of 7 pages Foreword SMPTE (the Society of Motion Picture and Television Engine
3、ers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Recommended Practices and Engineering Guidelines, are
4、prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and ITU. SMPTE Engineering Documents are drafted in accordance with the rules
5、 given in Part XIII of its Administrative Practices. SMPTE Recommended Practice RP 202 was prepared by Technology Committee C24. Introduction As bit-rate reduction has become pervasive in emission, contribution, and distribution of video content, multiple compression and decompression (codec) cycles
6、 are required. Concatenation of codecs may be needed for production, post-production, transcoding, or format conversion. Any time video transformations to or from the coefficient domain of macroblock-based algorithms are performed, care must be exercised in alignment of the video both horizontally a
7、nd vertically as it is coded from the raster format or decoded and placed in the raster format. Over multiple compression and decompression cycles, it is highly desirable to maintain the original positioning of the video signal within the raster. Less obvious, but just as important, is the need for
8、macroblock alignment to reduce artifacts among encoders and decoders from various equipment vendors. If concatenated encoders do not share common macroblock boundaries, then additional quantization noise, motion-estimation errors, and poor mode decisions may result. Likewise, encoding decisions that
9、 may be carried through the production and post-production process with recoding data present will rely upon macroblock alignment. Conforming to this practice will minimize artifacts in multiple generations of compression (bit-rate reduction) encoding and decoding by optimizing macroblock alignment.
10、 RP 202-2008 Page 3 of 7 pages 1 Scope This practice specifies the spatial alignment for video compression (bit-rate reduction) encoders and decoders, including but not limited to MPEG-2, MPEG-4 Part 10 (AVC) and SMPTE VC-1. Both standard-definition and high-definition video formats for production,
11、distribution, and emission systems are addressed. 2 Conformance Notation Normative text is text that describes elements of the design that are indispensable or contains the conformance language keywords: “shall“, “should“, or “may“. Informative text is text that is potentially helpful to the user, b
12、ut not indispensable, and can be removed, changed, or added editorially without affecting interoperability. Informative text does not contain any conformance keywords. All text in this document is, by default, normative, except: the Introduction, any section explicitly labeled as “Informative“ or in
13、dividual paragraphs that start with “Note:” The keywords “shall“ and “shall not“ indicate requirements strictly to be followed in order to conform to the document and from which no deviation is permitted. The keywords, “should“ and “should not“ indicate that, among several possibilities, one is reco
14、mmended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but not necessarily required; or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited. The keywords “may“ and “need not“ indicat
15、e courses of action permissible within the limits of the document. The keyword “reserved” indicates a provision that is not defined at this time, shall not be used, and may be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never
16、be defined in the future. A conformant implementation according to this document is one that includes all mandatory provisions (“shall“) and, if implemented, all recommended provisions (“should“) as described. A conformant implementation need not implement optional provisions (“may“) and need not im
17、plement them as described. Unless otherwise specified the order of precedence of the types of normative information in this document shall be as follows. Normative prose shall be the authoritative definition. Tables shall be next, followed by formal languages, then figures, and then any other langua
18、ge forms. 3 Normative References The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this sta
19、ndard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. SMPTE 274M-2008, Television 1920 x 1080 Image Sample Structure, Digital Representation and Digital Timing Reference Sequences for Multiple Picture Rates SMPTE 293M-2003, Televisi
20、on 720 x 483 Active Line at 59.94-Hz Progressive Scan Production Digital Representation SMPTE 296M-2001, Television 1280 x 720 Progressive Image Sample Structure Analog and Digital Representation and Analog Interface (R2006) RP 202-2008 Page 4 of 7 pages ITU-R BT.601-6 (01/07), Studio Encoding Param
21、eters of Digital Television for Standard 4:3 and Wide-Screen 16:9 Aspect Ratios ITU-R BT.709-5 (04/02), Parameter Values for the HDTV Standards for Production and International Programme Exchange ITU-R BT.1358-1 (09/07) Studio Parameters of 625 and 525 Line Progressive Scan Television Systems 4 Nome
22、nclature 4.1 Coding range: The range of coded lines and coded pels is referred to as the coding range. This practice does not differentiate between encoders and decoders. For any format in Table 1, encoders should compress the specified range. Likewise, decoders should decompress the stream and plac
23、e the video in the specified range. Therefore, regardless of encoding or decoding, the ranges for lines and pels are referred to as the coding range. 4.2 Coded lines: The specific vertical lines to be encoded, or where decoded video should be placed vertically. 4.3 Coded pels: The specific horizonta
24、l pels to be encoded, or where decoded video should be placed horizontally. 4.4 Format: The scanning format referenced by number of active lines. 4.5 Resolution: Two-dimensional definition of image space. Horizontal units of pels and vertical units of lines. 5 Recommended Coding Ranges Table 1 conta
25、ins the recommended coding ranges for bit-rate reduction encoders and decoders. Line and pel numbering for the various video formats shall be as defined in the normative references listed in Section 3. RP 202-2008 Page 5 of 7 pages Table 1 Recommended Coding Ranges for Various Video Formats Resoluti
26、on Coded lines Format Pels lines Coded pels Field 1 Field 2 Frame 480I 720 480 0-719 23-262 286-525 - 480P 720 480 0-719 - - 45-524 512I 720 512 0-719 7-262 270-525 - 512P 720 512 0-719 - - 13-524 576I 720 576 0-719 23-310 336-623 - 576P 720 576 0-719 - - 45-620 608I 720 608 0-719 7-310 320-623 - 60
27、8P 720 608 0-719 - - 13-620 720P 1280 720 0-1279 - - 26-745 1080I 1920 1080 (See Note 4) 0-1919 21-560 584-1123 - 1080P 1920 1080 (See Note 4) 0-1919 - - 42-1121 NOTES 1 Interchange between 480I and 480P, 512I and 512P, 576I and 576P or 608I and 608P video that has been encoded according to this pra
28、ctice will require a format conversion including vertical filter that provides appropriate transformation of the information to avoid improper alias, vertical location, and/or unnecessary loss of picture content. 2 Interchange of 480I video that has been encoded according to this practice with 480I
29、video that has been encoded using field-2 lines 285-524 will require a format conversion that provides appropriate transformation of the picture information to avoid improper vertical location and/or unnecessary loss of picture content. 3 Interchange of 576I video that has been encoded according to
30、this practice with 576I video that has been encoded using field-2 lines 335-622 will require a format conversion that provides appropriate transformation of the picture information to avoid improper vertical location and/or unnecessary loss of picture content. 4 In macroblock-based compression syste
31、ms that code in multiples of 16 lines, 1088 lines are actually coded. The additional eight lines are added at the bottom of the picture prior to encoding and are discarded after decoding. Table 2 Normative Reference Documents for the Formats of Table 1 Format Reference 480I, 512I, 576I, 608I ITU-R B
32、T.656 480P, 512P SMPTE 293M 576P, 608P ITU-R BT.1358 720P SMPTE 296M 1080I, 1080P SMPTE 274M RP 202-2008 Page 6 of 7 pages 6 Backward Compatibility 6.1 Vertical Alignment A large installed base of 480I and 576I equipment exists. Backward compatibility issues exist primarily for 480I relative to code
33、d ranges. Thus, in choosing the correct 480 lines to encode for 480I, generic legacy data on line 21 was accounted for, but not other vertical interval data on line 22, so the range coded was lines 22-261 and 285-524. Also, in some cases, a consumer product MPEG-2 decoder may expect that the encoded
34、 video it receives is shifted up a line from this recommendation. However, even on display devices that do not overscan, this will likely not be noticeable to the viewer. 6.2 Horizontal resolution modifications Some MPEG-2 encoders reduce the horizontal resolution of the video. Horizontal resolution
35、 reductions should occur only at the emission stage to ensure macroblock alignment during the production process. For applications where resolution reductions at the emission stage require significant changes in the number of pixels, the reduction will normally be performed with filtering and subsam
36、pling; hence, no horizontal macroblock alignment is expected. Examples would be resolution reductions from 720 pixels to 544 pixels or down-converting from HDTV to SDTV. For small resolution reductions in SDTV applications, cropping is often used in order to remove any blanking edge distortions that
37、 may be difficult for the emission encoder. An example would be a resolution reduction from 720 pixels to 704 pixels. Filtering and subsampling may also be used; however, neither method provides the desired horizontal macroblock alignment. Therefore, it is important that no resolution changes are ma
38、de prior to that required for the final emission encoding. RP 202-2008 Page 7 of 7 pages Annex A (Informative) Bibliography ISO/IEC 13818-2:2000, Information Technology Generic Coding of Moving Pictures and Associated Audio Information: Video ISO/IEC 14496-10:2005, Information Technology Coding of Audio-Visual Objects Part 10: Advanced Video Coding SMPTE 421M-2006, Television VC-1 Compressed Video Bitstream Format and Decoding Process
